1. Field of the Invention
This invention relates to guide rolls, and, more particularly, to a guide roll construction suitable for conveying hot workpieces, for example, in continuous metal casting operations, ingot-making operations or in an anterior stage of hot rolling in the steel-making industry or the like.
2. Description of the Prior Art
Conventional guide rolls of this sort are generally constituted by a steel roll shaft of unitary construction to ensure necessary strength and are internally provided with a cooling water passage for enhancing the heat resistance of the roll shaft. In some cases, for the purpose of increasing the thermal resistance, there have been used guide rolls with a heat resistance alloy surface or guide rolls of a composite construction having a sleeve or rings of heat resistant material integrally fitted on the circumference of the roll shaft. However, the conventional integrated type roll constructions are more or less unsatisfactory in heat resistance, in resistance to thermal shocks, in resistance to abrasive wear and mechanical strength which are essential for the guide rolls to be used for guiding workpieces of high temperature, in the absence of a unitary or composite material which can meet all of these requirements.
Further, in the continuous casting processes, there is an increasing trend toward energy conservation, retaining the heat of the hot cast stock while it is transferred after severing and utilizing its heat effectively in the subsequently hot rolling. In the continuous casting operation, the rolls which convey a continuously cast strip from a water-cooled mold to a shearing machine are subjected to a high temperature above 1000.degree. C. so that more severe conditions are imposed on this sort of guide rolls. In order to lessen thermal deterioration in strength which will shorten the service life of the rolls and to reduce the heat dissipation from the workpieces to the rolls, it has been proposed to use ceramic material with high heat resistance and a high heat insulating property, e.g., embedding the ceramic material in axial or circumferential grooves provided on the outer periphery of a roll shaft, or fixing pieces of a ceramic material on the circumference of a heat insulating cylinder which is fixedly fitted on the roll shaft. However, the conventional guide rolls of this sort invariably are complicated in construction or require complicated machining operations on the steel roll shaft itself or on the mounting pieces which fix the ceramic material on the roll shaft, coupled with problems such as the short service life of the mounting pieces due to thermal fatigue resulting from the exposure to the heat of the high temperature work and difficulty in repairing the rolls or replacing damaged ceramic material in a short time period.